Automatic party-line telephone-exchange system.



A. E. KEITH. AUTOMAHC PARIY LINE TELEPHONE EXCHANGE SYSTEM.

APPLICATION flLEP AUG.20 I906.

Patented June 11, 1918.

2 SHEETS-SHEET I.

N 192%??? for f A ex-an derZ IZa'ffi A. E. KEHH. AUTOMATIC PARTY L|N TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED AUG.20, I906- 1 pllwlilllllg/ Q ffizfl "n tunber.

sion ol :1

. ninxannnn E'. KEITH, OF CHICAGO, ILLINOIS,

T0 AUTOMATIC ELECTRIC company, A

ASSIGNOR, BY MESNE ASSIGNMENTS,

CORPORATION OF ILLINOIS.

AUTOMATIC PARTY-LINE TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented June 11, 1918.

Application filed August 20, 1906. Serial No. 331,343.

To all whom it may concern.

Be it known that I, ALI-maxim]: E. Kerr", a citizen of the l'nited States "of America, and resident of Chicago. (ook county. Illinois, have invented a certain new and useful Improvement in Automatic PartyLine 'lelephonc-Exchange Systems. of which the following is a specification.

My invention relates to telephone systems in whichautomatic switching. machinery is placed under the control of the sub scribers to enable a calling subscriber to automatically connect his line with that of the called subscriber, and in which several subscribers stations are located on one and the same line. lines of this character being ordinarily known as party lines; and it re lates more mrticularl v to telephone exchange systems in which the automatic switching machinery comprises selectors and connectors. and in which these automatic switches or niachinesare controlled or operated by electrical impulses trans mitted from the calling subscribers substation; and it contemplates more especially a telephone exchange system in which party line substations are combined with selectorsand connectors foetrunking and connecting in aceordance with a'n v called and with preliminary trunking mechanism by which preliminary trunking operations. are performed in advance of an trunking or connecting operations relative to the called number.

The object oi nv invention is the proviwhi h the part lines terminate in preliminary trunkingmachinery. and in which the requisite trunking and connecting operze tions are performed relative to the called 'numlzeigand subsequent to the prelili'iinary trunking (nu-ration; and the-provision of certain details and features oi improvement and combinations tending to increase the general ellirienev and improve theservice of a telephone exchange system of this particular character.

To the foregoing and other useful ends, my invention consists in matters litl'tll ltlftttl set forth and claimed.

in the tlt'tnlnpalt \'lll,2' drawings. Figure 1. is a diagram of a party line in which one oitlie subscribers has called back upon his own line. so to speak. to signal another subscriber on the same line, the signaled or telephone exchange system in called subscriber having answered. The central office apparatus comprised in the connection is indicated in this figure. The substations of the party line are also shown. In the said Fig. 1 the line switch allotted to the party line is imlicated at A. the ccntral battery at. 15,.the first-selector switch 5, the comieetor-switch (Y, the first party line station tll1 l) l'l)t* second station at E. and-the third station stations being shown.

A central battery is shown in each of the various drawings. but in practice there is but one batterv B havin; its positive terminal preferably grounded at (i.

The master switch for controlling all of the line switches of the group to which the line switch A belongs is shown at ll.

Fig. 2 is a more complete diag'rannnatic view of the line switch and ot its toaster switch ll.

Fig. 3 is a diagram of the line switch bank-wiring, two banks I and I bein 1 indicated. the left-hand section onl) of t te latter being shown:

Fig. 4 is an enlarged view of the master switch bank J.

In connection with the line switch (Fig. 1) only one of the trunk line terminals is shown. but ten of these trunk line terminals comprise the line switch bank I.

The substation may be of any suitable or approved general type. but the substation I) (Fig. I) is an improvement upon the substation equipments heretofore emploved. It is provided with a receiver 2 and a switclr hook 3. which is (.OlllPUst'llUf two parts t and 5 fastened together with the insulating liber 6 between the two parts. The member 4 has radiating from its body a number of cam-arms 7. 8. t), and 10 and from the member 5 the cam-arm 11 extends. said hook being pivotally secured to the keyboard frame (not shown) by the screw 12 about which it rotates when the receiver is removed. The rotation is due to the tension of a spring (not shown) and the hook is pushed up for the purpose of changing certain circuit connections. as will be explained. In addition, the substation has a transmitter 12 a local battery 14. a ringer 15. an induction-coil It; with a primary winding 17 and a secondary winding 18. a condenser 19, a signaling device composed of a push button :0, spring 21, two contact points 22 and 23,

at I only three suband a lock-out magnet 24. When the switch The switch-hook also carries a slimv rod 53,

thelower end 54 of which worksin front of the armature 47 and is bent at a right en le 1 horizontally and in a planexparqllel with t e (lenscr 19, said circuit being normallg I switch-hook is down the cam Qdepresses the All bridged across the line. Asspcietmi wi the spring 25 are two sets of springs 26 27 hes; normal position allowing the and 28, 29, 30. "Members of each of t sets, "when left to their own tensi0ntlmt s, when the switch-hook "is up-engnge in contact with each other; thesprings 26i and 27 are then in contact nnd'thesprings 28,

29,-. end 30 are in contact. But when the spring 25, and thisspring ew pepuits the springs; 26 and '27 to separate and et the.

same time 'forces the springsjgs, and? apart through the medium ctr-en insulating bushing 31 located between the s rings 25 and 30. The arm 8 when raised orces the spring 32 away from the spring 33, while the egg: 7 PQ1'I n'lt 5l/l1e spring 34, which is normally se aretcd from the spring 35, to close in con act with the letter. Whenever the switch-hook is drawn down the three springs 36, 37 and 38, which are known as release springs, are forced into engagement by the arm 10. This arm engages a laterally projecting piece at the top extremity of the spring 38 of this group of release springs; moreover, when the switch-hook nears its lowermost position the said arm disengages from the said springfiind permits the-three release springs to brezil; apart and re gain their ormel positiohsn The switch-hob in rising rings the arm 11 in contact with the.

spring 39, but only momentarily, form the switch-hook nears its uppermost position the arm 11 and spring 39 disengage. The calling device is represented by two push-buttons 40 and 41, two springs 42 and 43, two contact points is and 45, and the ground post 46. The lock-out me not consists of thecoil 24 mounted upon tie keyboard by a bracket, not shown. The armature 47, which carries ut its extremity an insulating bushin 48, is so constructed mechanically that wv enever themngnet is energized the springs 49 and 50. which nrc normally in contact, are then disengaged. Furthermore, said magnet carries on its under. side an armature locking device which consists prel? erebly of a brass piece 51 which is riveted to e spring 523ml which latter is in turn fastenedto the rear end of the magnet frame. The front end of this brass ieoeil is bent upwerdly at it right angle 21llllfl at a right angle to, the front, so that whenthe ennui tore {Us attracted by the magnet the spring tension-indie spring fihl; ioreestheflpiece I upwardly unt I ngled ci ifiii rises 'll'l lie ill? sud airiordingly it in it attracted position,

surfece of the armature.

lt will be nnder'stood their 'improvement in telephone is stems and, ap- $0 paratua, Serial 15703311 3327.

t is built about a -metallic base or frame snot shown) and consists of e plunger '55 an plunger arm 56, cut-oil relay 57, trip magnet 58 and switch release magnet 59. The said switch release magnet is provided with an armature 60 pivotally held by the pin 61 which rises from the base or frame of the switch. This armature is.held normall away from the magnet cores by any suitable spring 62. 0 The said-armature 60 carries, pivotally secured at its end, a second armature 63 that is controlled by the trip magnet 58, and

which is normally held away from the me?- net cores. of the trip magnet by any suitab spring 64. The pin 65 about which the armature oscillates is carried on theend of the armature 60. The plunger 55 is pivotally secured by the pin 66 to the plunger arm 56, I which latter is in turn pivoted to the pin 67 which rises from the base or frame of the i switch. Normally the lunger 55 is retained out of engagement with the biiili I and retaiued in en agement with the plunger controlling shn t 68 which is operated by the masterswitch H of the group to which this line switch A belongs. The force that causes the plunger 55 to be, thrust into the bank I whenever the trip magnet 58 is energized is supplied by the s ring 69, one end of which spring is SECUIfGt to the switch frame by nenns of the flange 70 while the other end is suitably retained at the rear end of the plunger arm 56. The plunger thus brought ll'lhOSGI'VlGfi may be restored by a hwmenta-ry 'energizetion of the switch release mngi not 59 (when the subscriber replaces his re ce lvfil' upon the hook), causing said inagneb 59 to attract its ermeturetO', thereby reising the'armnture 63 which then slips oi er'120h the end of, the plunger arm 56. As soon as the magnet becomes 'denergized the retract mg spring 62 restores the switch. release armature 6,0 to its normal positibn, at which time, of course, the plunger arm is false" drawnmto ROIII I BIlPOSIiLiOII and more i ack into engagement with the fiBJ t fierctmc" mien pfthe plignger shaft asoscilletoryf, imd

m sihettlielvesits eelstresses m 13 bushing 71 enters the pass to such after it has left the shaft, may to the said groove. As soon as the plunger bank I-the cut-01f relay 57 becomes energized, attracting its armature 72, which opens the contact formed by the springs 73 and 74. t

be master switch H is built upon a metallic frame or base and consists of a motor relay or magnet 75, an auxiliary relay 76 and a differential relay 77, a camcontrolling ratchet-wheel 78, and a wiper arm 79 comprising a cam 80 and a wiper 81. The ratchet-wheel 78 has four pro ecting cam-lugs 82. Said ratchet-wheel is pivotally supported by a pin 83. There is also a pawl 84 operating in connection with the ratchet which is kept in engagement with the teeth thereof by a retracting spring 85. The objectv of this pawl is to retain the ratchet-wln-el always in its advanced posilion and prevent any -backward rotation thereof. The power for rotating, said ratchctavlu-el is provided by a niotor mag net 75 which comprises two coils; It is provided with the armature 86 that carries the insulating bushing 87 for automatically opcrating the motor inagnet circuit interrupter comprising the springs 90, 91 and 92, and is also provided with an extending arm on the end of which is pivotally mounted the suitable spring Said pawl is normally held in the retracting spring 8!), one end the pawl supporting the rear end oithe pawl 88.

position by of which is secured to arm' and the other to pawl ilsclt'. retained away from the magnet cores by any (not shown). When in this normal position the spring til) holds the springs 91 and 92 in contact. The ener'izing circuit of said motor magnet comprises in series the springs 91 and J2, and when energized the magnet. of course, attracts its armature 86, at which time the bushing. 8? drives the spring 510 from under the spring 92, which latter then discngages from the spring Ell. thcrcby destroying the continuity of the energizing circuit through the motor magnet coils. At once the armature 86 returns to its normal position, the bushing 87 raising the spring 92 in contact with the spring H1 and permitting the spring W to hold lhe circuit closed through the motor magnet. 'ldnnfiillhtt operation occurs again and again as long gizcs the said motor magnct is retained in series with the motor magnet coils and the springs .ll and U2. it is obvious that each time the arnmturc tsl' is atlructcd the pawl H s driws lbc rntcln-I\\'l|ccl 78 around one st p in the direction indicated by the arrow,

In which position said tamed by the pawl HI. described and shown in ratchet-whecl is rc- Theinterrupter here a position that any plunger, not return I to the contact The armature 86 is normally.

as the battery that cncr- Figs. Land 2 is olh any suiiablc form or character.

mcnt of the ratchet-wheel 78 imparts motion to the cam by means of the cam lug 82,

which in turn gives to the plunger shaft' ,the hank contacts at each step and also the common contact plate, and thus the engaged contact of .J is always kept in electrical connection with the conunon plate 93 by the wiper 81. As shown in Fig. 4, the master switch bank J comprises the individual seg ments a separated from the common plate 93 by the fiber insulating strip 93. The insulated spring 92 is so arranged that when the wiper 81 moves to the last contact 94, and then on the next step is carried 94 on the right, the upper part of the wiper 8] slides upon the guide spring 92. This provision is made so that the wiper 81, Ill passing from one extreme position to the other, will not place the scgments 0 in contact with the common mem her 93, whereby some interference might he experienced with the master switch ll. The cam arm 80 and wiper arm 81 are so adjusted upon the plunger shaft 68 that. if one of the pins 82 engages the cam arm at apoint so that the wiperarm 81 engages one of the bank contacts 94, then when the ratchet-whee] advances one step the wipcr arm. by means of the cam 80 and lug 82. is advanced to engage the next hank contact 95. and for each consecutive position of the rateluet-wheel the wiper arm engages a succceding hank contact. The construction is such that. after the cam lug has traveled to the end of the cam, then at the next step of the ratchet-wheel the said cam discngagcs from the said lug and falls into engagement with the next succeeding lug. The force for thus carrying the cam onto the next lug 82 is supplicdby the coil spring 96. The action of the master switch is in general as follows: If: the subscriber I) by means of his line switch seizes on apreselected idle trunk line corresponding, for example. to the bank scgmenttll upon which it will be assluned the master switch wiper 81 is rest ing. he causes a. guarding potential to be established at the contact point 94 at the in slant that the plunger 55 seizes the said trunk line. The dill'crcntial relay 77 then becomes energized. pressing the springs 81 and 82 into contact, and closing a series circuit through the springs 91 and 92 and the motor n'iagnct 7n and the dili'ercntial relay springs 8'1 and 7'42. The motor magnet becomes energized and rotates thc ratchchwhccl one step. thereby moving the wiper arm 81 to the next contact ".7. The mptor magnet is thus again dci m-rgizcd and the armature Ho and interrupter springs 91 and )2 rcsumo their normal position. It will be seen to cause i shown his eralty e described in Patent No.815

219, 220, 221 and 222, respectively.

the subscribeg that the function of the master switch is i to at alltimes maintain the 'idle lungers in a positi opposite an idle trunk inc, and ril plungers that are released to instantly take a similar position.

The first-selector switch may be of any suitable or approved type, such as the genera] form of selector described in Patent No.

tails of thefirst-selector are well known, in-

the first-selector switch-shaft (not which carries the line wipers 211 and 212 and the private wiper 213. The side switch is controlled by the {private magnet 214,]and in the normal 'or rst position of the side switchthesidwswitch wipers 215, 216, 217 and 218 engage the contact oinlfs t e second osition the contact points 223, 221,

(i 226 areengaged, and 'in the third position the wipers engage the contact points 227," 228, 229 and 230, respectively. After the line switch has operated and a trunk leading to a first-selector has been seized the first-selector is then under control of the calling subscriber through the medium of the vertical and rotary line relays 231 and 232'. While the side switch is inthe first volving position the calling subscriber controls the 232 acting conjointly provide the means by which'the release magnet 235 is operated by while the side switch is in first or secon osition. If the side'switch passes to the third position, however, (since the selector S is of the trunk release type) the release magnet 235 is. then controlled through the connector C, and by way of the.

private wiper 213 and by means of the backrelease relay 236. V The connector-switch C mag be of any suitable .or approved form, suc

as the gen- 176, grant .March 13, 1906, to Keith', Ericlzson and Erickson. The mechanical details of the connector and selector, as is well known, are very much the same, although there is some material difference in the circuits. The connector-switchehaft which "is not shown) like the selector carries-the line wipers 101 and 102 and the private wiper 1,03. Their/onnector-switch is also controlledy the calling subscriber thro h'theme ium of' the vertical and rotary line relays 10-1and105,.

the springs 250 and 2419 23, guar: 7

means I p The vertical line relay 104 directly controls the vertical me not 106 and also the rotary magnet 107. he oflice of the magnet 106 is to give the shaft and shaft wipers their vertical movements, and the rotary magnet 107 imparts to said shaft and wipers a rotary or circular movement. The rotary line rela 105 controls the private magnet 108, whic latter under'certainconditions'in turn controls the vertical and rotary ma ets 106 and 107, the release magnet 109 an also the side switch wipers 110, 111, 112 and 113. The side switch has a normal or first osition, a second and a third-position. In t e normal position the respective side switch wipers en age the contact points 114,115, 116 and 11%; in second position the wipers engage the contact points 118, 119, 120 and 121;'

and in third position they engage the contact points 122, 123, .124 and 125. The release magnet 109 is also controlled by the line relays 104 and 105 acting, together. The connector divides the circuit that passes through it into two sections by the condensers 126 and 127; In addition the-connector has a ringer relay 128 by means of which the ringer generator 129 is bridged across the terminals of the called line to signal the called subscriber. Eachexchange has a busy signaling apparatus K of any suitable design, as, for example the one comprising an interrupter 130 in series with the primary winding 131 of an induction-coil132. The secondary winding 133 is connected .to the contact point 131 which presses against the switch shaft springs 135 when the normal post arm 136 10808.

The calling operation by which the subseriber D, for example, :would call and silg- ,nal the subscriber F is as follows: He (t calling subscriber). removes the receiver 2 from the switch-hook 3, thereby allowing the switch hook to rise and the cam 11 to engage the spring 39 momentarily. This engagement permits the trip magnet 58 to becomerenergized momentarily, thus attracting thearmature 63 which allows the plunger 55 to seize an idle trunk line leading to the first-selector. The circuit of this preliminary impulse is as to ws: from ground Gr through the conductor 137,, contact springs 50 and 49, conductor 138, springs 34 and35, conductors139 and 140 to the spring 39, cant-arm 1'1, conductors 141, 142 and 143 to the contact point 41, sprin 42, Fonduetors 144and 145, bridge-cut-o M relay, springs 73 and 74 tothe trip magnettf58, thence to thg springs 146 and 147 to the battery lead 14 undedterminal-of battery to he no itugro ,B and to grou G. When the plupger closes tial-is established attheconnr w for the protect on of the hneallotted to the lin swlmh l i po an al ten s om ground misses? 250 and 249 to the private normal conductor 169 which leads to the connector private bank. Also, an energizing circuit through the cut-off relay 57 is com 'leted, there y operating the said relay. T e armature of said relay separates the springs 73 and74 and thus disconnects the rotar line cohductor 144 from the line switch Furthermore, the line switch release magnet 59 is connected with the first-selector release relay spring 256, by we of the bank springs 257 and 258 and cont uctor 259, when the said springs 257 and 258 are pressed into engagement by the plunger. The calling subscribers su ation is now connected to the first-selector switch terminals or conductors 14!) and 150 as follows: The vertical line extends from the spring'43 of the calling device over the conductor 151, through the bank springs 152 and 153 to the vertical terminal 1-19 of the first-selector. The rotary line extends from the spring 42 of the cal-ling device over the conductors 144 and 154, through the bank springs 155 and 156 to the relay 97, through the winding of this relay to the rotary terminal 150 of the firstselector. Assume the number of this particular line to be #220; then to call the substation F the number 220 must be called by the subscribcr'D, since F occupies the line #220 in conimon with D, as also does o'lhefirst digit of the called number bein 2', and the receiver 2 having been removed from the switch-hook, the springs 26 and 27 close in contact, likewise the springs 28, 29

and 30, and the ground post 46 is in connection with the substation ground G" by the closing together of springs 34 and 35. The subscriber at substation D then proceeds to press the button 41 twice, corresponding to the numerical value of the digit. Hence, each time that the button 41 is pressed the spring 43 leaves the contact point 45 and is grounded orythe ound post 46, and as a result the verti'calhire relay 231 of the first- The current selector S is eergized once. for energizing aid relay flows from ground G through the'conductor 137 andsprings 50 and 49, conductor 138, springs 34 and 35, conductors 139 and 157 to the calling device ground post 46, conductor 151 and through ihc hank springs 152 and 153 and conductor 149 to the vertical line relay 231. through the winding of said relay and conductor 2&7 to the battery lead 148, to the non-grounded terminal of battery B and to ground G. Each time the vertical line relay 231 is energized the line relay springs 238 and 239 are pressed into-contact and 'an energizing circuit is thereby established each time through the vertical magnet 233. The circuit in said magnet flows from ground G through the line relay springs 239 and.23 8, onductor 240 to the private magnet prings 24] and 242, through the conductor 24%,

through the winding of the vertical magnet 233, conductor 244 to the battery lead 148,to thenon-grounded terminal ofbattcr y I3 and to ground (1 The vertical magnet operates to raise the switch-shaft (not shown) and wipers 211, 212 and 213. The vertical magnet being operated twice the first-selector shaft is raised two steps and said wipers 211, 212 and 213 are carried to a level with the contact points that constitute the terminals of the trunk line leading to the connector-switch C. After operating the ver tical button 41 with the above result the subscriber then presses the rotary button 40 once, grounds the rotary line conductor and as a result operates the rotary line relay 232 of the first-selector S. The path of the energizing current may be traced as follows from the substation ground G to the conductor 137, through the springs 50 and 49, conductor 138, springs 34 and 35 conductors 139 and 157 to the calling device ground post 46, through the spring 42 to the conductors 144 and. 154, through the bank springs 155 and 156, through the winding of relay 97, conductor 150 to the rotary line relay 232, through the winding of said relay to conductor 237, thence to the battery lead 148, to the non-grounded terminal of battery B and to ground G. The rotary line relay 232 upon energizing presses the line relay springs 239 and 245 into contact, establishing an energizin circuit through the private magnet 214. he current through said magnet passes from ground G through the springs 239 and 245, through the private magnet winding to the battery lead 148, thence to the non-grounded terminal of battery B and to ground G. The private magnet being energized fora moment the side switch of the first-selector switch passes to the second position, permitting the side -ground G through the side switch Wiper 218 to the interrupter springs 246 and 247, to the winding of the rotary magnet 234, to the battery lead 148, to the non-grounded terminal of battery B and to ground G. The rotary magnet is energized one step and the wipers 211, 212 and 213 carried into engagcment with the bank contacts that constitute the terminals of a trunk line leading to the connector-switch C, assuming that the trunk leading to said connector leads oil from the first set of contactsof the second level. But if the first trunk line is busy an energizing circuit is established through the private magnet 2H when thalprivate wiper 1 5 to call his own line. By means of the relay 9? the subscriber l) is permitted to call back on his own line. because the rotarv impulse Contact 122. thereb relay 10-1 in contro energizing shifts tho cal ling subscriber ceases energizes the relay 7 and separates the springs 99 and 100. thereby removing the guarding potential. momentarily.which allows the connector side switch to. pass to third position instead of roloasing the connector-switch on the last rotary impulse. thus placing the side switch wipers 110. 111, 112 and 113 in contact with the points 122. 123. 124 and rospeotivoly. In this particular instance the called subscriber and the callingsubscriber occupy the same line. and the first-selector switch and connector switch employed by the calling subscriber in response to the calling device select the line #220.

To signal the called subscriber the calling subscriber presses his signaling button 20, placing tho spring 21 in contact with ground and thereby energizing the vertical line relay 104. The path of tho energizing current is known. It will be remembered that the connector side switch has passed from the second to the third position. and the side switch wiper 110 is in engagement with placing the vertical line of the ringer relay 128 in tho same manner that the rotary magnet. 10? came under the control of the vertical line relay when the side switch wipers passed from first to second position. Therefore, when the vertical line relay 104- presses the springs 15!) and 160 into contact the ringer rclay 128 is energized by a flow of current from ground (1 through the springs 100 and 159, conductor 164, side switch wiper 110, contact point 122, conductor 170. through the ringer relay winding to the batterv lead 148. thence through battery It to ground i. The ringer relay 128 upon springs 171 and 175 from the springs 172 and 176 onto the springs 180 and 181. respectively. This results in separating the lines of the calling and called subscribers and bridging across the line of the latter the rin er generator 129. A signaling current is. t erefore. sent from the enerator 129 through the springs 180 and 1 1 and side switch wiper 113. mntaet point 125, conductor 170. shaft wiper 101, normal conductor 1'67. conductors 151 and 182m the impulse spring 183 of the signaling device. conductor 18% to the. switchhook 185 and cam-arm 186 to the spring 187. then through the substation bell 188. eon denser 189, through the rotary impulse spring 190 of the calling device, conductors 191. 144 and 15-1, normal conductor 168. shaft wiper 102. side switch wiper 112 to the ringer relay springs 175 and 181 and to the ringer generator 120. As soon as'tlle to press the signaling button 20 the ringer relay becomes deenergized and the. springs 171 and 175 again come in contact. with springs 172 and 170. respectively. It will be remembered that both substations E and F are in normal condition and that the signaling current which passed through substation F also passes through substation 1 1. A series of signals, say one ring for 1), two ring for E and three rings when substation F is called, has been previously understood between the different subscribers. and the subscriber at I" when the bell rings three times removes the re oeiver 192 from the switch-hook 103, thus bridging the secondary circuit that includes the said receiver and the secondary winding 104 of the induction-coil 19:: across the line. The lock-out relay becomes energized with results similarto those when the receiver at substation l: is removed. a descriptioncf whi h is hereinafter given. The bridging circuit is completed as soon as the switchhookpermits the springs 190 and 10? to come in contact. The local transmitter circuit is closed when the springs 198. 1!!!) and 200 engage in contact.- The two subscribers I and Dare now placed in communication over a'circuit which is entirely independent of the central office apparatus. the central otlico equipment in this particular case serving only to signal the called subscriber.

.\n intruding subscriber will be lookod out., lle can listeinin. but cannot disturb the'connect ions or use the line. i

The connection described being established. if a. subscriber at substation E removes. his receiver from the switch-hook, the look-out relay 201 will be operated so as to prevent a connection between the ground post ,202 or signaling button contact 203 or ground release spring 204' and ground terminal G. The switch-hook springs are so adjusted that the springs 204 and 205 which are normally disengaged when the switchllookis' down are thrown into contact as the switch-hook rises, before the spring you is separated from the spring 207. There is. therefore. andnstant when the S\\'lttl1-ll(ml( is rising in which a circuit through the loole onto-clay 201 is'completed. (.urrent then flows which energizes said relay, causing its armature to be attracted and locked. as previously described, thus separating the, springs 208 and 209 even after the energizing current of the lock-out relay has ceased to flow. The circuit of the energizing current maybe traced from ground G to the. springs 206 and 207. through the winding of the relay 201. springs 204 and 205, vertical conductors of the callin device, conductors 182 and 151,1ine swite hank springs 152 and 153. conductor 14!). side switch wiper 215, shaft wiper 211. conductor 24?, the vertical line relay 104 to the battery lead 148. thence to battery 1% and to ground (1. The sub-station ground G is then entirely out 130 mal con off from the calling device ground post 202,

signaling button contact 203 and ground release'sprin 204'. scriber at may work his ccllin or press his signaling button or ang up his receiver without interfering with the connection existing at the time. The subscriber D upon returning the receiver to the switch-hook restores the look-out relay 201 Consequently; the subto its normal condition-by means of the rod 210, as previously described.

The front release occurs when the subscriber restores the receiver 2 to the switch-hook 3, thereby ressing into connection for a moment to release springs 36, 37 and 38. The engagement of said release springs grounds the vertical and ro-. tary line conductors 151 and 144 simultaneously, thereby simultaneously energizin over well known circuits the vertical and rotary line-relays 104 and 105 of the connector C. This results in bringing the springs 253 and 254 into contact,.closing a release circuit through the back release relay 236 of thefirst-selector S and through the release magnet 109 of the connector C. The path of this circuit is as follows: from ground G to the side switch wiper217, to

.the back release relay winding 236, to the shaft private wiper 213- of the first-selector to the connector relay release springs 253 and 2254, release magnet 109 of the connector to the battery lead 148, thence through battcry B to ground G. When the connector release magnet 109 is thus supplied with current it energizes, andas a result the connector switch shaft and side switch are restored to normal position, thus breaking connection between the connector switch shaft wi ers 101, 102 and 103 and the noructors 167, 168 and 169. The back releaserelay 236 of the first-selector S be ing in the same circuit with the release magnet 109 (as shown) energizes simultaneously with the latter. The back release relay 236 of the first-selector upon energizing places the springs 255 and256 in contact, therebyclosing a circuit through the first-selector release magnet 235 and the line switch release magnet 59. The circuit, of the release magnet 235 extends from groui'id Gr through the springs 255 and 256 to the winding of the release magnet 235, to the battery lead 148, thence through battery B to'groun-(l G. The line switch-release magnet 59 is closed through a circuit extending from ground G", back release springs 255 and 256, conductor 259, bank springs 258 and 257, through thewinding of the line switch releasemagnet 59 148. thencethrough All of these release relays and magnet; attract their respective armatures and remain in roadiness'to soon as the substation release springs 36,

device calling.

same line can use the line to the battery lead. battery B to ground:

release the switches as 37 and 38 separate and break the ground connection to the line conductors 151 and 144-. The calling subscriber thus restores all the switching apparatus which he originally brought into use. To call any other subscriber the calling subscriber would bring about the same operations as described in calling #220. The successive digits of the desired number would be called in order, thus operating the first-selector S and connector C step by step, and placing the connector shaft wipers on the terminals of the called line. The energizing, guarding potential and releasing c'ircuits are known-in fact to call an other line an exact'repetition of the descri ed op eration would be required, and thusitwlll be seen that any subscriber connected with the central oliice may place himself in communication with any other subscriber, that any subscriber may call his own line-#that is, any subscriber on a party line-v-inalsmuch' as the connector switch Gused in this case will not be automatically released as when it engages -the multiple line termimil connected with the lineifrom which the call came, even if the private bank contact corresponding to the desired line is' unded. Furthermore, if one subscriber 18 using the party line no other subscriber on the for either switching orsignalin purposes. In other words, the two subscri ers who are conversing over the line are safe against intrusion or m'olestation to this extent, namel subscriber can use the line fbr switching or signaling purposes, nor'can any other subscriber on the same line so operate his telephone or switching devices as to endan er the continuity of the circuit established tween the two subscribers who are talking.

It is always an undesirable thing, of course,

to have it possible for one subscriber on a. line to listen in and hear the conversation conducted over the line by some other subscribers,

safety as against interference on the part of other subscribers on the line. would be out of the question. It is evident, however, that, myimproved loch-out arrangement and de vices are of a character to prevent a subscribcr from transmitting any signal, and from accomplishing the closure of my bin that no other 100.

cnits at the central station. if the line is already in use. As described. a calling subscriber never finds his own line so protected (by reason of his use of the line) that he may not himself call back upon his line, providing the line is not already in posses sion of some other subscriber; but if he calls another line said line may be busy. in which event the connector side switch will not pass to third position and establish the final connection. instead the connector switch is released at the instant that the callinr subscriber grounds his rotary line canduetor 114 after the connector wiper 103 has been carried onto a grounded private contaet. In that case the busy release takes place. whereby the connection is restored and the calling subscriber gets the busy signal.

The busy release follows as a result of the energization of the rotary line relay 105, if the called line is busy. as follows: The said relay 105 upon energizing ener izes the private magnet 108. as previous y described, which latter in turn presses the springs 251 and into contact; As soon as the said springs 251 and 252 engage. the release magnet 109 is placed in connection with the private wiper 103 (since the side switch wiper 111 is now in Second position and in engagement with contact point 119), which wiper 103 has been previously rotated onto a grounded contact. As a result a flow of current is sent through the release magnet 109 from the grounded private wiper 103 to the side switch wiper 111. thence through the contact point 119. private springs 251and' 252 to the release magnet 109. thence to the battery lead 148 and through battery B to ground G. The release magnet upon energizing releases the connector switch shaft and restores the connector side switch to its first position. returning the vertical magnet 100 to the control of the vertical line relay 104. Therefore. if the calling subscriber (Fig. 1) presses his signaling button 20 and grounds the vertical line conductor 151, he operates the vertical line relay 101. which latter in turn operates the vertical magnet 100. The vertical magnet raises the switch shaft so that the normal post arm 130 permits the switch shaft spring 135 to come in contact with the spring 134. and a busy signaling current is sent to the calling subscribers station. The circuit over which the busy signal passes is as follows: from the induction coil winding 133 of the busy machine K through the contact springs 134 and 135 to the side switch wiper 112, ringer relay springs 175 and 170. condenser 127, conductor 248. first selector shaft wiper 212, side switch wiper 216. conductor 150, condenser 97'. line switch bank springs 156 and 155, conductors 154. 144, and 143. condenser 10, receiver 2. secondary winding 18 of the induction-coil 16, through the vertical line the line switch and line of another and -inconductor bank springs 152 and 153, conductor 149. first-selector side switch wiper 215 to the shaft wiper 211. conductor 247, vertical line relay 101 of the connector to the battery lead 11-8, and thence again to the coil 132 of the busy machine K. The calling subscriber upon hearing the busy signal will understand that the desired line is busy and will release the switching apparatus (by hanging up his receiver) over the same circuits previously described. It will be clear, of course, that if the subscriber E called the subscriber N of any other line the normal conductors 167, 168 and 169 leading from the connector shaft wipers 101, 102 and 103 would not lead back and connect to the calling line switch A and line, but instead to dependent subscriber, in a manner well known to those skilled in the art.

The construction of the line switch bank I is fully shown in Fig. 3. It comprises a set of springs 249 connected together, or one common plate, and comprises also three other similar plates or sets of springs 257, 152 and 155. Allotted t0 the common member 2119 isa row of individual springs 250 each of which is adaptedto be thrust into engagement with the common member 249 separately. Likewise there is another row of individual springs 258 each adapted to be thrustseparately into engagement with a common member 257. Still another row of individual springs 156 is allotted to the common member 155. and another row of .individual springs 153 is allotted to the common member 152. It will be noticed that the several banks have a common member 240 connected in multiple, likewise the common member 257, the common member 152 and the common member 155. lso, similar springs of the various rows 0 individual springs are connected in multiple, as shown. The object in such a construction is to minimize the number of private normal relays 97.

In the system the relays and magnets may he of any suitable resistance. but good results are obtained when the private normal relay 97 is wound to a resistance of about sixty ohms.

From the foregoing it will be seen that I combine preliminary trunking machinery with automatic switches or machinery for subsequently trunking or connecting in accordance with all of the digits of any called number, and with telephone lines having a plurality of subscribers stations thereon that is to say, telephone lines which are ordinarily known as party lines, each .sub-

scriber on a line being provided with means CLO automatic switches or machinery by which trunking: and collili'tllitig operations are ac.- complished in itt'ltnltliillift with. all of the digits of any called number, each subscriber on a line bcin also capable of aulon'mtically calling any other subscriber on the same line through the medium of the said preliminary trunking machinery or individual switch X'lHClHtlllSlliF allotted to the difl'ercnt in telephone lines. It will also be seen that I have made certain changes and improvements in the substation equipments, in the individual switches or preliminary trunking machinery. and in the selectors, which latter are, of course, in the nature of firstselecto'rs inasmuch as they perform selectinn and trunking: operations in accordance.

with the first digit of any called number. \Vilh my improrcd apparatus it will be seen that any subscriber on the line can use the preliminary trunking mechanism for autoruatically trunking in advance of the Subsequent trunking and connecting, operations which correspond to the different digits of the called number. Furthermore, when one subscriber is using the line, and the indi vidual switch for the line is in use, no other subscriber on the line can operate his substation equipment in such manner as to disturb the already established connections.

'hat I claim as my invention i.s:-

1. In a tchnhone exchange system, the

combination 0 a telephone line, a ilurality of substations on said line, a preliminary trunking switch allotted to said line, trunk lines leadin, from said switch, automatic switching machinery to which Said trunk lines lead, and mechanism at the substations by which any subscriber on the line 40 can operate said automatic switching machinery in accordance with all of the digits of any called number, and subsequent to the automatic preliminary trunking operation by which the said individual switch extends the telephone line into connection with said automatic switching machinery, said mechanism returna le to normal position after each digit.

2. In a telephone exchange system, the combination of a telephone line, a plurality of suhscribere substations on said line, impulsc-transznitting mechanism, trunk lines, automatic switches by which any subscriber on the line may establish connections in accordance with all of the digits: of any called nun'iber, by a separate operation of said impulse-transmitting mechanism by the call.- in; subscriber for each digit. and preliminary trunking 'machinery by which any calling subscriber on the line seizes an idle trunk to obtain connection with one of said automaticswitches. 3. In in telephone exchange system, the combination of a telephone line, a plurality 66 of substations on said line, trunk lines, automaticincans by which any calling subscriber on said line obtains connection with a preselected idle trunk line, means by which each calling subscriber selects the next idle trunk line foe use by the next calling sub- 70 seribcr, and suitable means for switching and connecting in accordance with any called number. I

4. 1a a tele hone exchange system the combination 0 a telephone line, a plurality of mibscribers, substations on said line, an individual preliminary trunkin switch for said line, a master switch contro ling the operation of said individual switch, trunk lines, a selector anda connector, means at the substations for controlling the operations of said individual switch and master switch and for controlling the operations of said selector and connector, a lock out rela for each substation, and an energizing circuit for each relay under the control of said indi vidual switch.

5. In a -te le hone exchange system, the combination 0 a telephone line, a lurality of substations on said line, a pre iminary trunking switch allotted to said line, trunk lines leading from said switch, automatic switching machinery to which said trunk lines lead,'and means at the substations by which any subscriber on the line can operate said automatic switchin machinery in accordance with all of the digits of any called number and subsequent to the automatic preliminary trunking operations performed by the said individual switch, together with trunk release circuits, each trunk release circuit including a third conductor of one 0 said trunk lines.

6. In a telephone exchange system, the combination 0 a telephone line, a. plurality of subscribers substations on said line, trunk lines, automatic switches by Which any subscriber on the line may establish connections in accordance with all of the digits of any called number, and preliminary trunking machinery by which any calling subscriber on the line obtains connection with said automatic switches, together with trunk release circuits, each trunk release circuit including a third conductor of one. of said trunk lines.

7. In a telephone exchange system, the combination of a telephone line, a pluralit of substations on said line. trunk lines. autoinatic means: by which any calling sub b0 seribcr on staid line obtains connection with a preselected idle trunk line, means by which each calling subscriber selects the next idle trunk line for use by the next calling subscriber, and suitable means for switching' and connecting in accordance with any called number, together with trunk release circuits, each trunk release circuit including a third conductor of one of said trunk lines.

8. In a telephone exchange system, the

combination of a telephone line, a pluality of subscnbcrs' ubstations on vsaid line. an individual preliminary trunking switch for said line. a master switch controlling the 0pc trunk lines, a loclcout relay for each sub station, and an energizing circuit for each relay under the control of said individual switch.

9. In a telephone exchange system, the combination of a telephone line, a plurality of substations on said line, a preliminar' trunking switcluallotted to said line, trunir lineslleading from said switch, automatic switchin machinery to which said trunk lines leail, and means at the substation by which any subscriber on -'he'line can operate said automatic switching machinery in accordance with all of the digits of any called number and subsequent to the automatic preliminary trunking operation performed by said individual switch, together with automatic means for permitting any subscriber to call another substation on the same line by projecting ringing current over the two sides of the said telephone line in series.

10. In a telephone exchange system. the combination of a telephone line, a. plurality of subscribers substations on said line, trunk lines, automatic switches by which any subscriber on the line may establish connections in accordance with all of the digits 40 of any called number, and preliminary trunking mach nery by which any calling subscriber on the line obtains connection with said automatic switches, together with automatic means for pcrmittingany subscriber to call another substation on the same line by projecting ringing current over two sides of said telephone line in series.

11. In a telephone exchange system. the combination of a telephone line. a plurality of substations on saidline, trunk lines, automatic means'by which any calling subscriber on said line obtains connection with a preselected idle trunk line, means by which each calling subscriber selects the nextidle trunk line for use by the next calling subscriber, and suitable means for switching and connecting in accordance with any called number, together with automatic means for permitting any subscriber to call another substation on the same line.

12. In a telephone exchange system, the combination of a telephone line, a plurality of subscribers substations on said line, an

individual preliminary tltlltkl'l'tg switchfor said have, a master switch controlling the op (ration of said individual switch. trunk lines, a selector and connector. and means at the substations for controlling the operations of said individual switch and master switch and for controlling the operations of said selector and connector. together with automatic means for ermitting any subscriber to call anothersnlistation on the same line.

13. In a telephone exchange system. the combination of a telephone line, a plurality of substations on said line. a preliminary trunking switch allotted to said line. means for operating said switch upon the removal of the receiver from the hook, trunk lines leading from said switch. automatic switches to which said trunklines lead, means at the snbstati'onsby which any subscriber on the.

line can operate said automatic switches in subscriber on the line maycstablish connections in accordance withfall of the digits of any called number, preliminary trunking machinery operated upon the removal of .the receiver fronrthe book, by which any calling subscriber onthe line obtains connection with said automatic switches. and means including relays at the substations for preventing one subscribed on the line from interfering with a connection already established by another subscriber on the same line, said relays controlling the calling circuits. I10

15. In a telephone exchange system. the ombination of a telephone line, a plurality of substations onsaid line.v trunk lines, autovmatic means by which any calling subscriber on said line obtains connection with a preselected idle trunk line, means by which each calling subscriber selects the next idle trunk line. for use by the next.

calling subscriber, and suitable means for switching and connecting in accordance with anv called number.together with means inchiding relays at the, substations for preventing one subscriber on vthe line from interfering with a connection already established by another subscriber on the same me. e

16. In a telephone exchange system, the i combination of a telephone line, a plurality of subscribers substations on said line, ah individual preliminary trunking switch for means for preventing said line, a master switch controlling the operation of said individual switch, trunk lines, a selector and a connector, and means at the substations for controlling theoperations of said individual switch and master switch and or controlling the operations of said selector and connector, together with means including relays at the substations for preventing one subscriber on the line from interfering with a connection already established by another subscriber on the same line.

17. In a telephone exchange system, the combination of a telephone line, a lu'rality of substations on said line, a pre iminary trunking; switch allotted to said line, trunk lines leading from said switch, automatic switching machinery to which said trunk lines lead, mechanism at the substations by which any subscriber on the line can operate said automatic switching machinery in accordance with all of the digits of any called number subsequent to the automatic preliminary trunking operation erformed by the said individual switch, said mechanism returnable to normal after each digit, and automatic means {or preventing one subscriber on the line from disturbing or inter' faring with a connection already established by some other subscriber on the same line.

18. In a telephone exchange system, the combination of a telephone line, of subscribers substations on said line, trunk lines, automatic switches by which any subscriber on the line may establish connections in accordance with allof the digits of any called number, said switches having one motion to find a group and then another motion of the same element to find a line in the selected group, preliminary trunking machinery by which any calling subscriber on the line obtains connection with said automatic switches, and automatic one subscriber on the line from disturbingpr interfering with a connection established by some other sub 'scriber on the same line.

19. In a telephone exchange system, the combination of a telephone line, a lurality of substations on said line, trunk mes, auwhich any calling sub,- scriber on said line obtains connection with a preselcctcd idle trunk line,means by which" each calling subscriber selects the next idle trunk line for use by the next calling subscriber, and suitable means for switching and connecting in accordance with any called number, together with automatic means for [WE-Venting one subscriber on the line from disturbing or interfering with a connection already established by some other subscriber on the same line.

20. In a telephone exchange system, the combination of a, telephone line, a plurality of subscribers substations on said line, an

a plurality establish a talking circuit over its conducindividual preliminary trunkin switch for said lino, a master switch contro lin the op eration of said individual switci trunk lines, a selector and a connector, an means at the substations for controlling the operations of said individual-switch andmastcr switch and for controlling the operations of said selector and connector, together with automatic means for preventing one sub scriber on the line from disturbing or interfering with a connection already established by some other subscriber on the same line.

21. In a telephone exchange system, a party-line having a )lurality of substations thereon,a line switc common" to said substations, a normally open line conductor adapted to be closed by the operation of said line switch, and a relay adapted to be energized over said normally open line conductor after a subscriber at another substa- 85 tion has operated the common line switch and thereby closed the normally cipen line conductor.

22. In a telephone system, a'line, a trunk, a non-numerical switch for connecting said trunk and line, at protecting ground circuit for said line, means for closin it ,Whena connection is made between said trunk and line, and means for breaking said circuit temporarily without breaking the connection.

23. In a telephone system, a plurality of trunk lines, a non-numerical line switch for connecting with any one of said trunks to tors, and a relay allotted to each trunk line and individual thereto, said relay connected in series with one of said'talking conductors and a shunt circuit around said relay.

24. In a telephone exchange system, a line, a plurality of subscribers stations on said line, an automatic trunk selecting switch comprising a line switch bank provided with trunk lines leading therefrom, a spring common to all of said trunk lines, individual springs, one for each trunk line, each of said individual springs adapted to be independently pressed into engagement with the common spring, and a spring-actuating element ada ted to travel from one spring to another, or the purpose set forth,and aloekout relay for each substation controlled by said switch.

25. In a telephone exchange system, a line, a plurality of subscribers substations on said line, an automatic trunk so ting switch comprising a line switch ban provided with trunk lines leading therefrom, a. contact common to allot said trunk lines, individual springs, one for each trunk line, each of said springs adapted to be independently pressed into engagement with the oommon contact, and a spring-actuating element adapted to travel from one s ring to another, for the purpose set fort a lock-out; 130

relay for each substation, and an energizin circuit for each relay under the control 0 said. switch.

2G. in a telephone, exchange system, a line, a plurality of subscribers substations on said line, a switch for each line having a ,bank of contacts provided with trunk lines leading therefrom, a separate group of individual bank springs allotted to each trunk.

, spribers telephone lines, trunk lines less in 20 number than the subscribers lines, a private normal relay for each trunk line, and a private normal conductor for each subscribers line, any one of said private normal relays adapted to remove ground from any oncof said private HtJI'llHll roinluctors, for the pur pose sol forth.

in. An automatic tehihone exchange lcm, comprisin; a party line, suitable trunks, automatic means for selecting trunks ahead of the alls, means for seizihgahc preselected trunks. and automatic means for preventing interference between subscribers on the same line in the use of said trunking means, substantially as set forth.

29. In a telephone exchange system, the combination of a telephone line, a plurality of substations on said line, a preliminary trunking switch allotted to said line, trunk lines leading from said switch, automatic switching machinery to which said trunk lines lead, mechanism at the substations by which any subscriber on the line can operate said automatic switching machinery, in accordance with all of the digits of any called number, subsequent to the automatic preliminary trunking operation by which the said individual switch extends the telephone line into connection with said auto matic switching machinery, said mechanism returnable to normal after each digit, and

automatic means for preventing intertei cnce between subscribers on the samc'linc by the transmission of impulses.

30. In a telephone exchange system, the combination of a telephone line, a plurality of subscribers substations on said line, trunk lines. automatic switches by which any subscriber on the line may establish connections in accordance with all of the digits of any called number, said switches having both rotary and vertical motions, one motion to select a group and the other motion to find a line in the selected group, preliminary trunking machinery by which any callin'g subscriber on the line seizes an idle trunk to obtain connection with one or more of said automatic switches. and automatic means for preventing interferen e bet ween subscribers on the same line by the transmission of impulses. i

ill. In a telephone system, the olubinw lion of a party liue with a plurality ol' sulr scribcrs stations thereon, trunk lines, means by which each subscriber on the line i ll mg selects an idle trunk line for the next subscriber, and means by which each calling subscriocr on the partydinc seizes the preselected idle trunk line.

52. In a li'ilcpl'ione system, the combination of a party-line with a plurality oi subscribers stations thereon, trunk lines. means by which each subscriber on the line in calling selects an idle trunk line for the next subscriber, means by which each calling subscriber on the party-line seizes the pre selected idle trunk line, and automatic means for preventing interference between subscribers on the Same line by the transmission of impulses.

33. In a telephone system, a party linp having a plurality of subscribers stations thereon. other telephone lines. trunk lines, a common mechanism b" which each calling, subs riber selects an idle trunk line tor the next subscriber, an individual switch for the party line, subject to the control of all of the party-line subscribers, and means by which each calling subscriber on the partyline causes said individual switch to select the preselected idle trunk line.

34.. In a telephone system, a party-line having a plurality of subscribers stations thereon, other telephone lines, trunk lines, a common mechanism by which each calling subscriber selects an idle trunk line. for the next subscriber, an individual switch for the party line, subject to the control of all of thc party-line subscribers, means by which each calling subscriber on the party line causes said individual switch to select the preselected idle trunk line. and automatic means for preventing interference be tween subscribers on the same line by the transmission of impulses 35. In a telephone exchange system, the combination of a telephone line, a plurality of substations on said line, a preliminary trunking switch allotted to said line, trunk lines leading from said switch, automatic switching machinery to which said trunk lines lead, said machinery having one run-- tion to select groups or divisions of the exchange and another motion to connect with a line in any selected group or division, and mechanism at the substations by which any subscriber on the line can operate said automatic switching machinery, in accordance with all of the digits of any called number, subsequent to the automatic preliminary trunking operation pcri'ornu-d by and coli iiceti ng in accordance with any called .nvit'ch for said line having number, said means for switching and connecting having one motion to select groups or divisions of the exchange and another motion to connect with a line in any selected group or division.

37. In a telephone exchange system. the

combination of a telephone line. a plurality of subscribers substations on said line, an individual preliminary trunking switch for .fll l line, a. master switch controlling the operation of said individual switch. trunk lines, a selector and a connector. said selector and connector having one motion to He lect groups or divisions of the exchai'ige and another motion to eouueci with a line in any selected group or division, means at the substations for controlling, the operations of said individual switch and master switch and for controlling the operations of said selector and connector, a lookout relay for each substation, and. an energizing circuit for each relay under the control of said individual switch. 4

38. In a telephone exchange system, a party line, said line provided with a plurality of subscribers substations, a trunking a line switch bank provided with trunk lines leading tl'icrefrom. a spring common to all of said trunk lines. individual sprii'igs, one for each trunk line, each of saidindividua] springs adapted to be independently pressed into en gagement with the common spring, a ground at the substation, means controlled by said ground and having one motion to select groups or divisions of the exchange and another motion to connect with a line in any selected group or division, for the purpose set forth, a loelcout relay For each substa tion, and an energizing circuit for each relay under the control of said trunking switch. 7

39. In a telephone exchange. system, a party line, said line provided with a plurality of subscribers substations, a trunking switch for said line havin I a bank of contacts provided with trunk lines leading divisions of the exchange and another motion to connect with a line in anv selected group or division. for the purpose set forth,

a lock-out relay for each substation. and an encrgizin circuit for each relay under the control 0' said trunking switch.

4-0. In. a tcle ihone exchange system. the combination oi subscribers lines divided into groups, a. private normal for any suhscriber in a grou), normally, grounded, a private normal relay provided with means for removing ground from the private normat of any subscriber in a group, a ground at the substation, means controlled by said ground and having; one motion to select 8U groups or divisions of the exchange and another motion to connect with a line in any selected group or division, for the purpose set forth, and a line circuit for said relay.

41. In a telephone exchange system. sub seribera telephone lines, trunk lines less in nmnber than the subscribers lines. a privale normal relay for eaeh trunk line. a

p ivatc normal conductor for each sub seriher's line, any one of said private uormal relays adapted to remove ground from any one of said private normal condiictors, a ground at the substation, and means controlled hy said ground and having one motion to select groups or divisions of the ex .95 change andanother motion to connect with a line in any selected group or division for the purpose set forth.

42. The improved automatic party-line telephone exchange system comprising: autoinatxic means for selecting trunks ahead of the calls, means for seizing the preselected trunks. automatic means for preventing interference between subscribers on the same line by the transmission of impulses, a 1.06 ground at the substation, and means controlled by said ground and having one motion to select groups or divisions of the exchange and another motion to connect with a line in any selected group or division, substantially as set forth.

43. In a telephone system, a partydine, a plurality of subscribers substations on said line, a nonnumerical trunking switch individual to said line. common to the different substations thereon, a lock-out relay for I each substation, an energizing circuit for each relay under the control of said trunking switch, and means for enabling subseribers on other lines to control said switch.

44. In a telephone system, a party-line, means for preventing interference between different subscribers on, said line, a. nonnumerical I trunking switch individual to said line, common to the different subseribers, and means for enabling subscribers on other lines to control said switch.

45. In a telephone system a non-numeri abling-subscribers on other lines to control Said switch and one or more numerical Switches, all of said switches controllable over the line by any subscriber thereon.

46. In a telephone system, a non-numerical trunking switch individual to a partyline, c nmon to all the substations thereon, an aulziiipatic busy test for preventing an efi'ective connection with a busy line. means for temporarily rendering the busy-test inoperative when one subscriber calls another on the same line, and means for preventing interference between subscribers on the same line by the transmission of impulses.

47. In a telephone system, a partydine, a non-numerical trunking switch common to the different subscribers on said partyline, an automatic busy test for preventing an effective connection with a busy line, and means for temporarily rendering the busy-test inoperative when one subscriber calls another on the same line.

4-8. In a telephone system, a subscribers line, a trunk line, means for extending a talking connection from said subscribers line over said trunk line, a ground connection for preventing ,a connection being made with said subscribers line, and a relay in said trunk controlling said ground connection, said ground connection being pelrmanently connected to a spring of said re ay.

49. In a telephone system, a subseribefis line. a trunk line, me ns for extending a talking connection from said subscrihers line over said trunk line, a ground connection for preventing a connection being made with said subscribers line, a relay in said trunk controlling said ground connection, and a condenser in shunt of said relay to permit the passage of talking current therethrough 50. In a telephone system, a party-line, means for calling back on said line, means for placing a busy potential on said line, and means common to a plurality of lines for removing said busy potential.

vSigned by me at Chicago, Cook county, Illinois, this 15th day of August, 1906.

ALEXANDER E. KEITH.

Witnesses:

Eownno D. FALES, MICHAEL Sn'rrEn. 

